# Domain Driven Design (DDD)

### Model Driven Design:
1. Concentrate all the code related to the domain model in one layer and isolate it from the user interface, application, and infrastructure code.
2. It is important to divide the application into different layers such as:
- User Interface(Presentation Layer)
- Application Layer- doesnt contain business logic but hold the application task progress
- Domain Layer - heart of the system, state of the business objects is held here.
- Infrastructure Layer: supports communication between layers and does persistence work and also contain supporting libraries.

### Entities:
Objects with identity which remain same throughout the system and provide continuity. For eg: Bank Account for the Person Class.
There is performance implications in making all objects entities. There has to be one instance for each object.

### Value Objects:
These objects don't have any identity but is used to describe certain aspects of a domain are value objects.
They are highly recommended to be immutable. Being immutable and having no identity, Value Objects can be shared.





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